Quarterback Christian Ponder, shown here in Raiders training camp last summer, was signed by the 49ers on Tuesday. (Anda Chu/Bay Area News Group)

Christian Ponder is joining 2011 draft-class quarterbacks Blaine Gabbert and Colin Kaepernick, the latter of whom hasn’t thrown in 49ers practice for nearly a week because of shoulder tightness.

Ponder agreed Tuesday to a one-year contract, filling the roster spot of Thad Lewis, who went on injured reserve after tearing a knee ligament as the backup quarterback in Sunday’s exhibition-opening loss.

The 49ers had only two healthy quarterbacks — Gabbert and rookie Jeff Driskel — throw in Tuesday’s brief practice before they flew to Denver, where they’ll practice Wednesday and Thursday against the host Broncos ahead of Saturday night’s exhibition.

Neither general manager Trent Baalke nor coach Chip Kelly were available for comment, and Ponder’s deal was announced an hour after media access to players ended.

Ponder did not play last season after going 14-21-1 as a starter from 2011-14 with the Minnesota Vikings. He was the No. 12 overall draft pick in 2011, two spots after Gabbert went to the Jacksonville Jaguars and 24 spots ahead of Kaepernick’s selection to the 49ers.

Last year, Ponder was with the Raiders in their offseason program and through training camp before getting cut Sept. 5. He resurfaced with the Denver Broncos in late November, was inactive for two games and was released Dec. 8.

One of Ponder’s best games with the Vikings came in a 2012 win over the visiting 49ers. He threw two touchdown passes and ran for a touchdown in a 24-13, Week 3 victory against the eventual NFC champions.

Ponder’s services were desperately needed by the 49ers considering Lewis is done for the season and Kaepernick hasn’t attempted a pass since last Wednesday’s practice at Kezar Stadium.

Quarterbacks coach Ryan Day helped throw in warmups during Tuesday’s walk-through practice, which lasted less than 90 minutes and was their first session held this training camp inside Levi’s Stadium.

Kaepernick may not be throwing but he is being allowed to participate to an extent in full team drills. That featured two handoffs to Mike Davis as well as Kaepernick running himself on a zone-read play during the three snaps he took with the second-string unit.

Gabbert, after completing only 4-of-10 passes in Sunday’s exhibition-opening loss to the Houston Texans, didn’t fare any better in his return to the Levi’s Stadium field. He was just 2-of-6 in full-team drills, when two targeted receivers weren’t looking for the ball and Garrett Celek dropped a pass.

Gabbert had a pass intercepted by Gerald Hodges in the end zone during a seven-on-seven, red-zone session, when Gabbert apparently thought Vance McDonald was going to run a different route.

— Of the 12 quarterbacks drafted in 2011, the first two ahead of Ponder were Cam Newton (No. 1, Carolina Panthers) and Jake Locker (No. 8, Tennessee Titans). Also in that class were Andy Dalton (No. 35, Cincinnati Bengals) and Tyrod Taylor (No. 180, Baltimore Ravens; current Buffalo Bills starter).

— No matter the quarterback drama engulfing the 49ers, running back Carlos Hyde is their projected offensive catalyst, and he knows he can’t repeat what he did Sunday. Uncharacteristically, Hyde fumbled.

“I can’t let that happen, and definitely not a scoop-and-score,” said Hyde, whose fumble was returned by the Texans for a touchdown and 7-0 lead in the 49ers’ eventual 24-13 loss.

Hyde has lost only one fumble in 198 carries in his two-year career. “He hasn’t been a fumbler. He’s not a fumbler,” running backs coach Tom Rathman said. “And we’ve been emphasizing it big time.”

Hyde wasn’t carrying the ball loosely when it got knocked from his grasp. Christian Covington got credited for forcing the fumble, but both Hyde and Rathman said nose tackle Vince Wilfork’s hip dislodged the ball.

Hyde, in his first game action since Oct. 22, ran for 22 yards on the carry preceding the fumble. “I’ve been out a while because of my (foot) injury, so I’m just trying to get back in the groove of things and get that game-feel back,” Hyde said.

— Wide receivers Quinton Patton, Bruce Ellington and DeAndre Smelter did not participate in team drills. Ellington had his legs stretched by a trainer in warmups. While Patton may have had the day off to rest, Smelter is believed to have a leg injury that will sideline him all week.

— Cornerback Dontae Johnson appeared to injure his wrist late in practice.

— Safety Eric Reid returned to the team after tending to the birth of his second daughter.

— Team owner John York attended practice for the first time this camp.

— Wide receiver Eric Rogers posted on social media a picture of himself heading into apparent surgery for his torn ACL.